Low-pressure processing system for magnetic orientation of thin magnetic film

ABSTRACT

A sputtering apparatus for depositing a thin film ( 66 ) of magnetic material on a substrate ( 26 ) is modified to include a plate-shaped electromagnet ( 34, 44 , or  70 ) for orienting magnetic domains within the film ( 66 ). The electromagnet ( 34, 44 , or  70 ) has conductive windings ( 38; 46, 48 , and  50 ; or  72 ) that are arranged for producing a magnetic field ( 42  or  52 ) within a plane ( 60 ) corresponding to a surface of the substrate ( 26 ). Field strength vectors ( 68 ) vary in absolute magnitude between points located along a first axis ( 62 ), but have substantially uniform components of magnitude at the same points measured in a common direction along the first axis ( 62 ).

RELATED APPLICATIONS

This application is a continuation application of allowed parentapplication Ser. No. 08/843,148, filed Apr. 25, 1997 now U.S. Pat. No.5,902,466, by Kevin S. Gerrish, Paul H. Ballentine, Dorian Heimanson,and Alan T. Stephens II, entitled SPUTTERING APPARATUS WITH MAGNETICORIENTING DEVICE FOR THIN FILM DEPOSITION. This parent application is aDivisional application of Application Ser. No. 08/369,381, filed Jan. 6,1995, by the same inventors, entitled MAGNETIC ORIENTING DEVICE FOR THINFILM DEPOSITION AND METHOD OF USE, now U.S. Pat. No. 5,630,916. Thisgrandparent application is a Continuation-In-Part of application Ser.No. 08/025,261, filed Mar. 2, 1993, now abandoned by the same inventors,entitled MAGNETIC ORIENTING DEVICE FOR THIN FILM DEPOSITION, which hasbeen abandoned. All prior related applications are hereby incorporatedby reference.

FIELD OF INVENTION

The invention relates to sputtering apparatus for depositing thin filmsof magnetically orientable material on substrates and to vacuumprocessing apparatus for magnetically orienting the material on thesubstrates.

BACKGROUND

Conventional sputtering devices include a vacuum chamber enclosing atarget electrode of selected material and a substrate onto which thematerial is to be deposited. Air within the chamber is evacuated to alow pressure and is partially replaced by an ionizable gas, such asargon. A power supply applies a negative potential to the targetelectrode. Gas ions strike the target, causing an emission of atoms fromthe target into a plasma from which the target material is deposited onthe substrate.

In certain applications, such as the manufacture of magnetic recordingheads, thin films of magnetic material need to be applied with apredetermined magnetic orientation. The thin films are deposited bysputtering apparatus in a predetermined orientation by exposing thesubstrate to a uniform magnetic field (i.e., equal magnitude field linesextending in a common direction). Ordinarily, permanent magnets placedin the vicinity of the substrate are used to generate the magneticfield.

For example, most commercial implementations locate a pair of permanentmagnets on opposite sides of the substrate to generate the requiredfield across the substrate. However, only a small portion of themagnetic field between the electromagnets exhibits the necessaryuniformity, and this limits the area of the substrate over which thetarget material can be deposited with the required magnetic orientation.

U.S. Pat. No. 5,026,470 to Bonyhard et al. discloses an alternativelydesigned sputtering apparatus having a polygon-shaped electromagnetlocated beneath the substrate. A spiral coil having a plurality of sidesforming a polygon is embedded in a pallet assembly for producing aplurality of uniform magnetic fields that extend perpendicular to eachof the sides. A plurality of substrates is positioned on the palletassembly with respective edges aligned with one of the sides. However,this apparatus is very large, difficult to manufacture, and inefficientto operate with smaller lot sizes.

After coating and subsequent processing, the substrates are cut intosmaller units that are used for such purposes as heads for disk drives.An industry trend now requires larger substrates (e.g., 15.25centimeters squared) to be coated with more accurately aligned magneticdomains (e.g., within one degree alignment). The increased accuracyprovides improved yield from the substrate, and the increased area ofthe substrate permits more heads to be manufactured simultaneously.

The larger substrates are difficult to coat with the present designs ofsputtering apparatus. For example, the permanent magnets located ateither side of the substrate must be spaced at large distances toproduce the required uniformity. However, the added spacing requiresimpractically large magnets be used to produce the required fieldstrength. Similarly, interferences between magnetic fields on each sideof the pallet assembly of Bonyhard et al. can significantly limit thesize of substrates that can be coated with accurately aligned magneticmaterial.

Although a uniform magnetic field is required in the vicinity of thesubstrate for magnetically orienting particles of the target material asthey are deposited on the substrate, the same magnetic field in thevicinity of the target can cause uneven erosion of the target andvariations in the thickness of deposited target material across thesurface of the substrate. The magnetic field reacts with an electricfield in the vicinity of the target causing emitted electrons to driftacross the target and to increase local ionization and accompanyingbombardment of one end of the target.

The sputtering device of Bonyhard et al. provides for rotating thepallet assembly to provide a more uniform coating of the target materialon the substrates. However, this adds to the size and complexity of thedevice and requires the use of uniformity shields which cut off part ofthe sputtered flux in order to produce a uniform film deposition.

SUMMARY OF INVENTION

The invention improves sputtering of thin magnetically oriented films byenabling large substrates to be coated with accurately aligned magneticdomains. A highly uniform magnetic field is produced in the vicinity ofa substrate with a practically sized and powered electromagnet. Theinvention also provides for depositing magnetic material with a uniformthickness across substrate surfaces without adding significant size orcomplexity to the new apparatus and without using shields to cut offpart of the deposited flux.

The improved sputtering apparatus includes the usual features of avacuum chamber enclosing a target electrode and a substrate holder madefrom a nonmagnetic material. A substrate is mounted on the holder with aprepared surface facing away from the holder. The electromagnet islocated just outside of the vacuum space adjacent to the holder andincludes a plate-shaped core and a series of parallel windings that aredistributed between two ends of the core.

The electromagnet produces a uniform magnetic field within a definedarea of a plane located at a predetermined distance from theelectromagnet corresponding to the location of the prepared surface ofthe substrate. The magnetic field is defined by a locus of fieldstrength vectors that vary in absolute magnitude but have substantiallyuniform components of magnitude (e.g., within a tolerance of fivepercent) within the defined area of the plane. The uniform components ofmagnitude are also aligned in a uniform direction within the same areaof the plane to produce a so-called “easy” axis of magnetization on thesubstrate surface that varies from uniformity by as little as plus orminus one degree.

This high degree of accuracy is obtained over a large area of thesubstrate surface (e.g., over 15 centimeters squared) by speciallyarranging the windings of the electromagnet on the plate shaped core.For example, the windings can be divided into groups for carryingdifferent amounts of current. More current is carried by the windingsclosest to the two ends of the core to compensate for changes in thestrength of the magnetic field close to the ends. The current withineach group of windings is adjusted to produce the uniform components offield strength in the uniform direction along the easy axis ofmagnetization across the entire surface of the substrate. In addition,the current can be adjusted to compensate for the buildup of magneticmaterial on the substrate or elsewhere in the vacuum chamber, which canincreasingly shunt the desired magnetic field.

Similar results can be obtained by varying the density of the windingsbetween the two ends of the core. For example, the windings can bearranged with increasing numbers of winding layers approaching the twoends of the core to appropriately vary the resulting magnetic field.Improved directional uniformity is obtained by specially shaping a coreof the magnet to further compensate for variations in the magnetic fieldat both ends of the magnet.

However, we have also discovered that magnetically permeable fieldshapers can be positioned next to the substrate to greatly increase thearea of the substrate surface that can be magnetically oriented with agiven size electromagnet. The field shapers are made of a paramagneticmaterial that is specially shaped and oriented to align a much largerportion of the magnetic field to a uniform direction.

The invention also provides for minimizing the harmful effects of themagnetic field on the target to provide a more uniform coating thicknessacross the substrate. For example, the plate-shaped electromagnet can bepowered by an alternating current that periodically reverses thedirection of the magnetic field. The alternating current has a cyclerate less than 10 hertz to prevent the formation of significant eddycurrents in the electromagnet core.

DRAWINGS

FIG. 1 is a schematic side view of a sputtering apparatus arranged inaccordance with the invention for coating a substrate with magneticmaterial.

FIG. 2 is a side view of a plate-shaped electromagnet for use in thesputtering apparatus of FIG. 1 having three separately powered windingsfor varying the strength of the magnetic field across the substrate.

FIG. 3 is a plan view of a plane corresponding to a surface of thesubstrate within which the magnetic field is defined.

FIG. 4 is a plan view of an alternative plate-shaped magnet having asingle-powered winding arranged on a stepped core in progressive layers.

FIG. 5 is an enlarged broken-away side view of the electromagnet of thepreceding figure showing a divided core and an increasing number ofwinding layers approaching one end.

FIG. 6 is a schematic side view of the sputtering apparatus of FIG. 1with field shapers mounted on an alternative substrate holder andelectromagnet assembly.

FIG. 7 is a top view of the alternative substrate holder showing theorientation of the field shapers with respect to the substrate andelectromagnet.

FIG. 8 is a bottom view of the alternative substrate holder showing anangularly adjustable mount for the electromagnet.

FIGS. 9A and 9B are schematic plan views of two magnetic fieldsgenerated by the electromagnet independently and in conjunction with thefield shapers.

DETAILED DESCRIPTION

One example of the invention is shown in FIG. 1 as a modification ofconventional sputtering apparatus. A vacuum chamber 10 has an outletport 12 connected to a pump 14 for evacuating air from the vacuumchamber 10 and an inlet port 16 for admitting an ionizable gas, such asargon, from a pressurized source 18.

Projecting within the vacuum chamber 10 are an electrode 20 supportingmagnetic target material 22, such as permalloy in concentrations of 81percent nickel and 19 percent iron, and a holder 24 made of anonmagnetic material for supporting a substrate 26. The target electrode20 is connected to a high voltage radiofrequency (r.f.) power supply 28for bringing the target electrode 20 to a negative potential. A biasvoltage can also be applied to the substrate 26 by similar conventionalmeans (not shown) for better controlling sputtering processes.Insulators 30 and 32 respectively isolate the target electrode 20 andthe substrate holder 24 from the vacuum chamber 10.

In accordance with the invention, an electromagnet 34 is positioned asclose as possible to the substrate 26 without being within the spaceevacuated by the vacuum chamber 10 to avoid outgassing effects fromelectromagnetic components and to make servicing easier. Theelectromagnet 34 has a plate-shaped core 36 made of a magnetic material,such as cold rolled steel, and conductive windings 38 that are wrappedaround the core 36.

Overall, the electromagnet 34 has the geometric form of a rectangularparallelepiped. Each side of the electromagnet 34 is at least fiftypercent larger than a corresponding side of the substrate 26. A powersupply 40, connected to the conductive windings 38, is sized to producea magnetic field 42 in the vicinity of the substrate 26 of about 30 to100 gauss. Preferably, the magnetic field 42 is applied completelyexternally of the vacuum chamber 10 to minimize the number of componentswithin the vacuum chamber 10.

FIG. 2 shows an alternative plate-shaped electromagnet 44 having threeseparately powered windings 46, 48, and 50 for producing a combinedmagnetic field 52. Respective currents in the three windings 46, 48, and50 are independently controlled by three power supplies 54, 56, and 58.The windings 46 and 50 along the ends of the electromagnet 44 carry morecurrent than the winding 48 at the center of the electromagnet tocompensate for changes in the magnetic field 52 approaching the ends ofthe electromagnet.

The magnetic field 52 is produced within a given area of a plane 60,corresponding to a surface of substrate 26, at a predetermined distancefrom the electromagnet 44. The plane 60, outlined in FIG. 3, has firstand second orthogonal axes 62 and 64. The first orthogonal axis 62,which corresponds to the desired “easy” axis of magnetic film 66deposited on the surface of substrate 26, extends perpendicular to adirection of the windings 46, 48, and 50; and the second orthogonal axis64, which corresponds to the film's so-called “hard” axis, extendsparallel to the same windings. The magnetic field 52 is defined by alocus of field strength vectors 68 that vary in absolute magnitudebetween points located along the first axis 62.

However, the respective currents in the windings 46 and 50 are adjustedwith respect to the current in the winding 48 so that the field strengthvectors 68 have substantially uniform components of magnitude (e.g.,within a tolerance of five percent) measured in a common direction alongthe first axis 62. The field strength vectors 68 also have substantiallyzero components of magnitude measured in a common direction along thesecond axis 64. In other words, excluding components normal to the plane60, the magnetic field 52 has a uniform magnitude and directionthroughout the area of the plane 60 for producing an average alignmentbetween domains of the deposited film 66 within one degree of perfectalignment with the easy axis—a condition referred to as “uniaxialanisotropy”.

FIGS. 4 and 5 show another alternative plate-shaped electromagnet 70 forproducing a similar magnetic field within the plane 60. Although asingle-powered winding 72 is used to produce the magnetic field, windingdensity is varied to compensate for changes in the magnetic fieldapproaching ends 74 and 76 of the electromagnet 70.

A magnetic core is formed by inner and outer plates 78 and 80 havingrespective face steps 82, 84 and 86, 88 approaching the end 74 foraccommodating multiple layers of windings without changing the externalshape of the magnet. For example, face steps 82 and 86 are formed to acommon depth that accommodates two layers of windings, and core steps 84and 88 similarly accommodate three winding layers. A symmetricalarrangement of steps and winding layers approaches the other end 76.

The sides of the core plates 78 and 80 are also stepped to achieve moreuniform directional accuracy within the plane 60. For example, firstside steps 90 and 92 and second side steps 94 and 96 are formed on theopposite sides of inner and outer core plates 78 and 80 to compensatefor variations in the magnetic field within the plane 60 adjacent to thecorners of the electromagnet 70. A symmetrical arrangement of steps alsoapproaches the end 74 of the electromagnet.

Although the sides are shown with just two discrete steps approachingeach of the ends 74 and 76, more steps could also be used to bettercompensate for the continuous variations at the magnet's corners. Infact, it would be possible to shape the sides of the core plates 78 and80 with smooth curves, but steps are still preferred for wrapping thewinding 72 in fixed positions.

The inner and outer core plates 78 and 80 are made of a magneticmaterial, such as cold rolled steel, which shunts the effects of thewindings crossing the outer core plate 80 on the magnetic field in thevicinity of the substrate 26. A space separating the two core plates 86and 88 permits a network of nonmagnetic conduits 98 to be positionedwithin the electromagnet 70 for circulating coolant to remove heatgenerated by operation of the electromagnet. This arrangement obviatesprior practices of machining similar passages in the core, which coulddistort the resulting magnetic field.

Referring again to FIG. 1, the magnetic field 42, which is required toorient magnetic domains of the film 66 deposited on the substrate 26,can also interact with an electrical field close to the target electrode20 and bias an ion plasma toward one end of the target electrode 20.Electrons emitted from the target electrode 20 for exciting the ionplasma are shifted along the target electrode in a direction defined bythe cross product of the interacting magnetic and electrical fieldvectors. The resulting uneven erosion of the target electrode 20 cancause variation in the thickness of the deposited film 66.

However, this problem is overcome by arranging the power supply 40 toproduce alternating current power for energizing the electromagnet 34. Alow pass filter 100 is connected in line with the alternating currentpower supply 40 to eliminate harmful effects of radiofrequency voltagefluctuations on the power supply.

The alternating current periodically reverses the direction of themagnetic field 42 but does not affect the desired alignment of the filmdomains along the easy axis of magnetization. Preferably, a cycle rateof less than one hertz is used in a square wave form to prevent unevenaccumulations of film 66 on the substrate due to the directionalinteraction of the magnetic and electrical fields near the targetelectrode. However, cycle rates up to ten hertz can be used for moreevenly depositing the magnetically orientable material without producingsubstantial eddy currents in the electromagnet core. As an additionalcontrol over the deposition process, the relative duration of thepositive and negative portions of the alternating current cycle can bevaried.

Although the invention has been described with distinct examples ofelectromagnets, different features of the examples can be combined witheach other. For example, the side steps 90, 92, 94, and 96 of theelectromagnet 70 could be formed in sides of the electromagnet 44, toachieve similar results. The electromagnet 44 could also be made withtwo magnetic core plates separated by nonmagnetic cooling conduits. Inaddition, both magnets 44 and 70 could be powered by the alternatingcurrent power supply of electromagnet 34.

FIGS. 6-8 illustrate an alternative embodiment including another way ofenlarging the effective area of the magnetic field and a way of changingthe orientation of the magnetic field with respect to the substrate. Asimilar electromagnet 110 is carried in a nonmagnetic tray 112 that ispivotally attached to a bottom of a substrate holder 114 by screws 116.The tray 112 has flanges 118 with arcuate slots 120 that permit angularmovement of the tray 112 with respect to the screws 116 throughapproximately 10 degrees. A vernier 122 provides a measure of theangular orientation of the electromagnet 110 with respect to a substrate124.

Similar to the preceding embodiments, the electromagnet 110, which islocated outside of the vacuum chamber 10, produces a magnetic field 126inside the vacuum chamber 10 having special characteristics within agiven area of a plane 128 that is coincident with a surface of thesubstrate 124 on which a film 134 of magnetically orientable material isdeposited. The magnetic field 126 within the given area of the plane 128is defined by a locus of field strength vectors that vary in absolutemagnitude between points located along a first of two orthogonal axes130 and 132 but have substantially uniform components of magnitude atthe same points measured in a common direction along the first axis 130.The field strength vectors have substantially zero components ofmagnitude measured at the same points along the second axis 132. Therelative angular position of the two orthogonal axes 130 and 132 withrespect to the substrate 124 is measured by the vernier 122.

Mounted on the substrate holder 114 adjacent to the substrate 124 withinthe vacuum chamber 10 are four field shapers 140, 142, 144, and 146 madeof a magnetically permeable material such as cold rolled steel. Thefield shapers 140, 142, 144, and 146 are shaped and positioned forenlarging the given area of magnetic field 126 that is effective fororienting magnetic domains of the deposited film 134 on the substrate124. As a result, larger areas of magnetic material can be oriented witha given size electromagnet.

Each of the field shapers 140, 142, 144, and 146 is L-shaped includinglong and short orthogonal arms 150 and 152. The long orthogonal arms 150are oriented parallel to orthogonal axis 130, which corresponds to theso-called “easy” axis of the deposited film 134. The short orthogonalarms 152 are oriented parallel to orthogonal axis 132, which correspondsto the so-called “hard” axis of the deposited film 134. The fieldshapers 140 and 142 are mirror symmetrical with the field shapers 144and 146 about the first orthogonal axis 130. The field shapers 140 and144 are mirror symmetrical with the field shapers 142 and 146 about thesecond orthogonal axis 132.

FIGS. 9A and 9B illustrate two different magnetic fields 156 and 158 inthe plane 128 produced by the electromagnet 110 independently and inconjunction with the field shapers 140, 142, 144, and 146. Boundary 160represents the area of the electromagnet 110 projected into the plane128.

In FIG. 9A, the magnetic field 156 is shown as it might appear withoutthe field shapers 140, 142, 144, and 146. Magnetic lines of force 162become increasingly curved with distance from the axis 130. Boundary 164defines a useful area of the magnetic field 156 within which themagnetic field lines 162 are skewed less than a predetermined tolerance,preferably two degrees. However, the useful area 164 represents only asmall portion of the area 160 of the electromagnet 110, e.g., less thanten percent. Accordingly, the required electromagnet size can becomeimpractically large for processing some substrates.

FIG. 9B shows the intended magnetic field 158 produced by theelectromagnet 110 in conjunction with the field shapers 140, 142, 144,and 146. The field shapers 140, 142, 144, and 146 increase magneticpermeability of particular regions in the plane 128 to better alignmagnetic lines of force 166 with the axis 130. Boundary 168 defines themuch larger useful area of the magnetic field 158 produced by the fieldshapers 140, 142, 144, and 146. Preferably, the field shapers 140, 142,144, and 146 are arranged so that the useful area 168 encompasses atleast one-third of the electromagnet area 160.

For example, a 9.25 by 9.25 inches plate-shaped electromagnet was foundto produce a useful area measuring only 2.0 by 2.0 inches. However,after adding four L-shaped field shapers, the useful area increased to6.0 by 6.0 inches. The four field shapers were made out of cold rolledsteel to 0.125 inches thickness with a width of 0.25 inches. The twoarms measured 1.5 inches and 4.0 inches, respectively. When assembled,the field shapers formed the corners of a rectangle measuring 7.5 inchesby 8.5 inches and were spaced from the electromagnet by 0.375 inches.The surface of the substrate was positioned midway of the field shaperthickness. Different size electromagnets could be similarly scaled.

We claim:
 1. A method of magnetically orienting a film on a substratecomprising the steps of: mounting a substrate on a substrate holderwithin a low-pressure processing space of a vacuum chamber; mounting atarget of magnetically orientable material within the low-pressureprocessing space of the vacuum chamber; mounting an electromagnetadjacent to the substrate holder outside the low-pressure processingspace of the vacuum chamber; aligning the substrate holder and theelectromagnet in different positions along a common axis so that thesubstrate holder is located along the axis in a position between thetarget and the electromagnet; powering the electromagnet with analternating current at a cycle rate less than ten hertz; and using theelectromagnet to produce a uniaxial magnetic field oriented parallel toa surface of the substrate for aligning magnetic domains of amagnetically orientable material on the substrate surface.
 2. The methodof claim 1 in which the substrate holder has a first surface within thelow-pressure processing space of the vacuum chamber and a second surfaceoutside the low-pressure processing space in which said step of mountingincludes mounting the electromagnet adjacent to the second surface ofthe substrate holder and remote from the first surface of the substrateholder.
 3. The method of claim 2 in which said step of aligning includesaligning the target with the substrate holder and the electromagnetalong the common axis.
 4. The method of claim 1 in which said step ofpowering the electromagnet includes powering multiple coils of theelectromagnet.
 5. The method of claim 4 in which said step of poweringalso includes directing different amounts of current to the multiplecoils of the electromagnet for more precisely aligning the magneticdomains of the magnetically orientable material on the substratesurface.
 6. The method of claim 1 in which said step of poweringincludes powering the electromagnet at a cycle rate less than one hertzfor controlling a distribution of the magnetically orientable materialon the substrate surface.
 7. The method of claim 1 in which said step ofpowering includes powering the electromagnet with an alternating currenthaving positive and negative portions with different durations.
 8. Themethod of claim 1 in which said step of powering includes powering theelectromagnet with an alternating current having a square wave form. 9.The method of claim 1 including the further step of sizing a core of theelectromagnet larger in area than the surface of the substrate measuredin a plane parallel to the substrate surface.
 10. The method of claim 1including the further step of orienting a plate-shaped core of theelectromagnet parallel to the substrate surface.
 11. The method of claim10 including the further step of varying a thickness of the plate-shapedcore between a center and two ends to compensate for uniformityvariations of the uniaxial magnetic field.
 12. The method of claim 1including the further step of positioning field shapers within themagnetic field out of contact with both the electromagnet and thesubstrate.
 13. The method of claim 12 including the further step ofarranging the field shapers so that they are L-shaped in a planeparallel with the substrate surface.
 14. A method of magneticallyorienting a film on a substrate comprising the steps of: arranging asubstrate holder with a first surface within a low-pressure processingspace of the vacuum chamber and a second surface outside thelow-pressure processing space; mounting a substrate on the first surfaceof the substrate holder within a low-pressure processing space of thevacuum chamber; mounting a target of magnetically orientable materialwithin the low-pressure processing space of the vacuum chamber; mountingan electromagnet adjacent to the second surface of the substrate holderoutside the low-pressure processing space of the vacuum chamber andremote from the first surface of the substrate holder; powering aplurality of windings of the electromagnet; and distributing adjustableamounts of electrical current between the windings for aligning magneticdomains of a magnetically orientable material along a magnetic axis on asurface of the substrate.
 15. The method of claim 14 in which theelectrical current is distributed between the windings in a ratio thatreduces skew of the magnetically orientable material from the magneticaxis with respect to a skew associated with an even distribution of theelectrical current between the windings.
 16. The method of claim 14 inwhich said step of distributing adjustable amounts of electrical currentproduces a magnetic field in the vicinity of the substrate surfacecontaining field lines that are skewed from the magnetic axis by no morethan two degrees throughout an area occupied by the substrate.
 17. Themethod of claim 14 including the further step of aligning the substrateholder and the electromagnet in different positions along a common axisso that the substrate holder is located along the common axis in aposition between the target and the electromagnet.
 18. The method ofclaim 17 in which said step of aligning includes aligning the targetwith the substrate holder and the electromagnet along the common axis.19. The method of claim 14 including the further step of wrapping thewindings around different portions of a common core.
 20. The method ofclaim 19 in which the windings are wrapped in a common direction aroundthe common core.
 21. The method of claim 14 in which said step ofpowering includes powering the electromagnet with an alternating currentat a cycle rate less than ten hertz for controlling a distribution ofthe magnetically orientable material on the substrate surface.
 22. Themethod of claim 21 in which said alternating current cycles betweenpositive and negative directions with unequal durations for furthercontrolling the distribution of the magnetically orientable material.23. The method of claim 14 including the further step of sizing a coreof the electromagnet larger in area than the surface of the substratemeasured in a plane parallel to the substrate surface.
 24. The method ofclaim 14 including the further step of orienting a plate-shaped core ofthe electromagnet parallel to the substrate surface.
 25. The method ofclaim 24 including the further step of wrapping separate windings arounda middle and each of two ends of the plate-shaped core.
 26. The methodof claim 25 in which said step of distributing adjustable amounts ofelectrical current between the windings includes distributing differentamounts of electrical current to the windings around the middle and bothends of the plate-shaped core.
 27. A low-pressure processing system formagnetically orienting a film on a substrate comprising: a vacuumchamber; a substrate holder within a low-pressure processing space ofsaid vacuum chamber; a target of magnetically orientable material withinsaid low-pressure processing space of the vacuum chamber; anelectromagnet mounted adjacent to the substrate holder outside saidlow-pressure processing space of the vacuum chamber; said substrateholder and said electromagnet being aligned in different positions alonga common axis so that said substrate holder is located along said axisin a position between said target and said electromagnet; saidelectromagnet being oriented to produce a uniaxial magnetic fieldparallel to a surface of the substrate mounted on said substrate holderfor aligning magnetic domains of a magnetically orientable material onthe substrate surface; and a power supply that powers the electromagnetwith an alternating current at a cycle rate less than ten hertz toenable a uniform deposition of the magnetically orientable material onthe substrate surface.
 28. The system of claim 27 in which saidsubstrate holder has a first surface within said low-pressure processingspace of the vacuum chamber and a second surface outside saidlow-pressure processing space, and said electromagnet is mountedadjacent to said second surface of the substrate holder and remote fromsaid first surface of the substrate holder.
 29. The system of claim 28in which said target is also aligned with said substrate holder and saidelectromagnet along said common axis.
 30. The system of claim 27 inwhich said electromagnet includes a plurality of separately poweredcoils.
 31. The system of claim 30 in which said power supply providesfor directing different amounts of current to said separately poweredcoils for more precisely aligning the magnetic domains of themagnetically orientable material on the substrate surface.
 32. Thesystem of claim 27 in which said power supply provides for powering saidelectromagnet at a cycle rate less than one hertz for controlling adistribution of the magnetically orientable material on the substratesurface.
 33. The system of claim 27 in which said power supply providesfor powering said electromagnet with an alternating current havingpositive and negative portions with different durations.
 34. The systemof claim 27 in which said power supply provides for powering saidelectromagnet with an alternating current having a square wave form. 35.The system of claim 27 in which said electromagnet includes a core thatis sized larger in area than the substrate surface measured in a planeparallel to the substrate surface.
 36. The system of claim 27 in whichsaid electromagnet has a plate-shaped core oriented parallel to thesubstrate surface.
 37. The system of claim 36 in which a thickness ofsaid plate-shaped core varies between a center and two ends tocompensate for uniformity variations of the uniaxial magnetic field. 38.The system of claim 27 further comprising field shapers positionedwithin the magnetic field out of contact with both the electromagnet andthe substrate.
 39. The system of claim 38 in which said field shapersare L-shaped in a plane parallel with the substrate surface.
 40. Anapparatus for magnetically orienting a film on a substrate comprising: avacuum chamber; a substrate holder having a first surface within alow-pressure processing space of said vacuum chamber and a secondsurface located opposite of said first surface outside said low-pressureprocessing space; an electromagnet mounted adjacent to said secondsurface of the substrate holder outside said low-pressure processingspace of the vacuum chamber and opposite of said first surface of thesubstrate holder; said electromagnet including a plurality of separatelypowered windings; and a power supply arrangement that adjustsdistributions of electrical current between said windings for aligningmagnetic domains of a magnetically orientable material of a surface ofthe substrate.
 41. The apparatus of claim 40 in which said power supplydistributes the electrical current between the windings in a ratio thatreduces skew of the magnetically orientable material from a magneticaxis with respect to a skew associated with an even distribution of theelectrical current between the windings.
 42. The apparatus of claim 40further comprising a target of magnetically orientable material withinsaid low-pressure processing space of the vacuum chamber.
 43. Theapparatus of claim 42 in which said substrate holder and saidelectromagnet are aligned in different positions along a common axis sothat said substrate holder is located along said common axis in aposition between said target and said electromagnet.
 44. The apparatusof claim 43 in which said target is also aligned with said substrateholder and said electromagnet along said common axis.
 45. The apparatusof claim 42 in which said power supply arrangement provides for poweringthe electromagnet with an alternating current at a cycle rate less thanten hertz for controlling a distribution of the magnetically orientablematerial on the substrate surface.
 46. The apparatus of claim 45 inwhich said alternating current cycles between positive and negativedirections with unequal durations for further controlling thedistribution of the magnetically orientable material.
 47. The apparatusof claim 40 in which said windings are wrapped around different portionsof a common core.
 48. The apparatus of claim 47 in which said windingsare wrapped in a common direction around the common core.
 49. Theapparatus of claim 40 in which said electromagnet includes a core sizedlarger in area than the surface of the substrate measured in a planeparallel to the substrate surface.
 50. The apparatus of claim 40 inwhich said electromagnet has a plate-shaped core oriented parallel tothe substrate surface.
 51. The apparatus of claim 50 in which saidseparately powered windings are wrapped around a middle and each of twoends of the plate-shaped core.
 52. The apparatus of claim 51 in whichsaid power supply arrangement provides for distributing differentamounts of electrical current to the windings around the middle and bothends of the plate-shaped core.